In Perl, how do I create a hash whose keys come from a given array?

Question

Let\'s say I have an array, and I know I\'m going to be doing a lot of \"Does the array contain X?\" checks. The efficient way to do this is to turn that array into a hash, wher

Answer 1

You can place the code into a subroutine, if you don't want pollute your namespace.

my $hash_ref =
  sub{
    my %hash;
    @hash{ @{[ qw'one two three' ]} } = undef;
    return \%hash;
  }->();

Or even better:

sub keylist(@){
  my %hash;
  @hash{@_} = undef;
  return \%hash;
}

my $hash_ref = keylist qw'one two three';

# or

my @key_list = qw'one two three';
my $hash_ref = keylist @key_list;

If you really wanted to pass an array reference:

sub keylist(\@){
  my %hash;
  @hash{ @{$_[0]} } = undef if @_;
  return \%hash;
}

my @key_list = qw'one two three';
my $hash_ref = keylist @key_list;